This invention relates to a magnetic head for magneto-optical recording having a slide contact member configured for being moved radially of a magneto-optical disc in sliding contact therewith for recording information signals in a magneto-optical recording and/or reproducing apparatus.
There has hitherto been employed a magneto-optical disc recording and/or reproducing apparatus employing a magneto-optical disc having a magneto-optical recording layer formed by a perpendicular recording film on a light-transmitting, transparent substrate.
With the magneto-optical disc recording/reproducing apparatus, an optical pickup device for radiating a light beam for illuminating the magneto-optical recording layer of a magneto-optical disc is arranged facing one of the major surfaces of the magneto-optical disc rotated by a disc rotation mechanism, while a magnetic head device for applying an external magnetic field to the magneto-optical recording layer is provided facing the opposite major surface of the magneto-optical disc. Thus the optical pickup device and the magnetic head device are arranged with the magneto-optical disc in-between.
With the magneto-optical disc recording/reproducing apparatus, a magnetic field whose direction is modulated in accordance with recording information signals is applied by a magnetic head device on the magneto-optical recording layer of the rotating magneto-optical disc, at the same time as a light beam outgoing from the optical pickup device is radiated on the magneto-optical recording layer. The portion of the magneto-optical recording layer which has lost its coercivity by being illuminated with the light beam so as to be thereby heated to higher than the Curie temperature is magnetized in accordance with the direction of the magnetic field applied by the magnetic head device. The light beam is relatively moved with rotation of the magneto-optical disc so that the above portion of the magneto-optical recording layer is no longer illuminated with the light beam and hence its temperature becomes lower than the Curie temperature. The information signals are recorded by fixation of the direction of magnetization.
With the conventional magneto-optical disc recording/reproducing apparatus, the magnetic head is caused to face the magneto-optical disc without being contacted therewith during recording of the information signals with a view to prohibiting the magneto-optical disc from becoming damaged by sliding contact with a metal core, such as a ferrite core, constituting the magnetic head.
Thus the conventional magnetic head device is provided with an electro-magnetic control mechanism for displacing the magnetic head in following up with surface deviations of the magneto-optical disc for holding the magnetic head at a pre-set distance from the magneto-optical disc without being contacted therewith even if a surface deviation has been incurred during rotation of the magneto-optical disc due to warping or thickness fluctuations in the disc.
With the magnetic head device provided with the electro-magnetic control mechanism for displacing the magnetic head in following up with surface deviations of the magneto-optical disc for holding the magnetic head at a pre-set distance from the magneto-optical disc, the electro-magnetic control mechanism needs to be driven by electric power, thus increasing the power consumption. In addition, a detection mechanism for detecting the distance between the magnetic head and the magneto-optical disc is required, thus complicating the mechanism for controlling the magnetic head device. In addition, the recording/reproducing apparatus becomes complex in construction thus rendering it extremely difficult to reduce the size and thickness of the apparatus itself.
Thus a magneto-optical disc recording/reproducing apparatus has been proposed in which a magnetic head device adapted for being slidingly contacted with the magneto-optical disc liable to produce surface deviations during rotation is provided in place of the magnetic head device adapted for controlling the magnetic head so as to be at a pre-set distance from magneto-optical disc.
With the magnetic head device employed in this sort of the magneto-optical recording and/or reproducing apparatus, a magnetic head element is mounted on a slide contact member having a sliding contact with the major surface of the rotated magneto-optical disc for maintaining a pre-set distance between the magnetic head element and the magneto-optical disc.
The magnetic head element, mounted on the slide contact member, has a magnetic core formed of a hard material, such as ferrite. If this magnetic core is directly contacted with the magneto-optical disc, the magneto-optical disc is damaged easily. Thus the slide contact member carrying the magnetic head element has a slide contact portion on its surface having a sliding contact with the magneto-optical disc. The slide contact portion is protruded from the distal end of the magnetic head element so that only this slide contact portion is contacted with the magneto-optical disc while the magnetic head element is not contacted with the magneto-optical disc. A magneto-optical disc 1 having sliding contact with the slide contact member carrying the magnetic head element has a magneto-optical recording layer 3, a reflective film 4 formed of a metal material such as aluminum and a protective film 5 formed of a UV curable resin, layered in this sequence, on one of the major surfaces of a disc substrate 2 formed by molding a light-transmitting transparent polycarbonate resin, as shown in FIG. 1. The magneto-optical recording layer 3 is formed by a first dielectric layer, a recording magnetic layer and a second dielectric layer.
The protective layer 5 is provided for prohibiting the magneto-optical recording layer 3 or the reflective layer 4 from being mechanically damaged and from becoming eroded by moisture or oxygen. The moisture or oxygen, attacking the magneto-optical recording layer 3 or the reflective layer 4, are intruded at the outer peripheral edge of the magneto-optical disc. Thus the protective film 5 is increased in film thickness at an outer peripheral edge 1a for positively covering the magneto-optical recording layer or the reflective layer 4.
If the outer peripheral edge of the protective film 5 is increased in film thickness, the magneto-optical disc is increased in thickness at the outer peripheral edge more significantly than at the inner peripheral edge, such that the major disc surface slidingly contacted by the slide contact member of the magnetic head device presents an inclined surface section 5a inclined from the inner periphery towards the outer periphery of the disc. Thus, when the slide contact member is moved towards the outer periphery of the magneto-optical disc 1, the portions of the magnetic head element other than the slide contact portion are contacted with the major surface of the magneto-optical disc 1, while the slide contact portion is spaced apart from the major surface of the magneto-optical disc 1. If the slide contact portion of the slide contact member is spaced apart from the major surface of the magneto-optical disc 1, the distance between the magnetic head element and the magneto-optical recording layer 3 cannot be maintained constant, such that correct recording of information signals becomes infeasible.
In addition, if the slide contact portion of the slide contact member is spaced apart from the major surface of the magneto-optical disc, thee is a risk that part of the magnetic head element be contacted with the magneto-optical disc 1 thus damaging the protective layer 5. If the protective layer 5 is damaged, the magneto-optical disc 1 tends to be attacked by water or oxygen, such that the magneto-optical recording layer 3 or the reflective layer 4 cannot be protected sufficiently.